1. Field of the Invention
This invention relates to sustained release pharmaceutical compositions and more particularly it relates to sustained release pharmaceutical compositions containing at least one drug in both an inner compressed core and an outer sugar layer.
2. Description of the Related Art
During the past few years there has been much work devoted to the development of systems which promote the release of active ingredients over a prolonged period of time. The advantages of administering orally active drugs in a sustained release formulation are numerous. If a drug is released too quickly in the stomach it can conceivably cause stomach upset. Additionally, the acid environment of the stomach may adversely affect the potency of a drug. Also the taking of medication once a day instead of numerous times a day eliminates a major source of inconvenience for the patient as well as providing for a more even distribution of drug concentration in the blood.
One example for the need for sustained release formulations is in the case of 1-(isopropylamino)-3-(1-naphthyloxy)-2-propanol(propranolol) described in U.S. Pat. No. 3,337,628. This compound is used in the treatment of coronary artery disease, migraine, anxiety, and tremors, and specifically as a .beta.-adrenergic blocking agent. However, a major drawback of compounds disclosed in U.S. Pat. No. 3,337,628 and particularly propranolol is that because of extensive metabolism, little unchanged active material reaches the systemic circulation after oral administration. Additionally, plasma levels of propranolol show a large patient to patient variation. The preparation of a sustained release formulation containing propranolol would allow for less frequent dosing while achieving similar blood levels to those attained by administering smaller doses more frequently.
U.S. Pat. No. 4,138,475 describes a sustained release composition containing propranolol which consists of a hard gelatine capsule containing film coated spheroids. The present invention relates to a new sustained release composition which is not disclosed in, nor rendered obvious by, either of the above cited patents, nor elsewhere in the art.